Super short workouts sound fantastic. Who wouldn't want to pack 60 minutes worth of exercise into 20—or sometimes even less? We've discussed quite a few, but not a lot about what you can expect while doing them. Amby Burfoot, writing for Runner's World, decided to take a look at the numbers.

You lead busy a life, and finding time to stay healthy is tough. Fortunately, all you need is 20…
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You can't get 60 minutes worth of calorie burn from seven or four minutes worth of exercise.

The math doesn't even come close. Any runners who exchange their four-times-weekly six-mile runs for four seven-minute workouts are going to burn at least 1000 fewer calories per week. Which will lead to a weight-gain of 12+ pounds in a year. Minimum. In one year. Try multiplying that by a couple of years.

And if you gain 12+ pounds a year, there's no way your endurance fitness or health is going to be better than it is today. No way. So what exactly have you gained by following a "scientific 7-minute program"? Beats me, though I think you'll probably have stronger quads, if that turns you on.

Shorter workouts can do a lot for your muscles, but if you seek weight loss you really need a good diet you can follow and exercise that will provide sufficient calorie burn. Eating fewer calories is the simplest way to reduce weight/fat, and compact exercise routines can help build muscle, but you shouldn't expect them to make you slimmer. You'll only get more bang for your buck with that approach. Otherwise, you have to put in the time.